This invention is concerned with monoclonal antibodies useful to detect humans who are susceptible to attacks of rheumatic fever. It is concerned also with methods of producing and using such antibodies, compositions containing them, hybridoma cell lines useful for producing them and diagnostic kits containing them.
The techniques for producing hybridoma cell lines and monoclonal antibodies utilizing mouse myeloma cells and spleen cells from immunized mice were first described by Kholer and Milstein in Nature 256, 495 (1975). Subsequently considerable effort has been expended in the production of new cell lines and monoclonal antibodies. The general techniques applicable to such production are well known and understood. However, knowledge of the procedures is not a guarantee of success. There are many difficulties and unexpected impediments. In fact, there is no assurance, prior to attempting to prepare a given hybridoma, that it will produce antibody if obtained, or that the antibody produced will have the desired specificity. The degree of success depends on the type of antigen employed, the fusion technology applied, and the selectin techniques used for identifing and isolating the hybridoma with the desired specificity which subsequently must be maintained by long term culture technology.
Individuals susceptible to attacks by rheumatic fever presently constitute a large segment of the world population. In India there are an estimated 8 million new cases of rheumatic fever per year, in Mexico there are 3 million cases, and in Africa 10 million. At least 60% of these individuals will ultimately develop serious chronic heart disease.
There is strong evidence to suggest that there is a particular B-cell alloantigen, the occurrence of which is significantly associated with patients who develop rheumatic fever, Patarroyo, Manuel E. et al, Streptococcal Diseases And The Immune Response, Academic Press, 1980, page 369. The occurrence of this alloantigen in unaffected, apparently normal individuals, and its inheritance in unaffected family members of patients provides evidence of the genetic nature of the alloantigen.
Briefly, the evidence for the existence of the alloantigen is the fact that a serum, designated serum 883, isolated from a multiparous woman in Bogota, Columbia, correctly identified 70 to 75% of all documented rheumatic fever subjects from different geographical areas of the world.
Rheumatic fever attacks in susceptible individuals are sequelae of streptococcal sore throats. In the present state of the art for preventing rheumatic fever attacks, documented sore throats as evidenced by positive cultures and rise in streptococcal antibody are treated with penicillin for ten days either by mouth or by injection. The reason for this procedure is that failure to heal the streptococcal infection during this period of time may result in rheumatic fever in 3% of the age group (5 to 18 years) at greatest risk.
At the present time there is no procedure for discovering those who are at risk of contracting the disease prior to the actual rheumatic fever attack. Fortunately, after the acute attack, subsequent attacks can be prevented by placing the patient on daily prophylaxis and penicillin. Clearly, it would be a valuable addition to the physician's armamentaruim if they could identify the susceptibles at birth. If the genetic marker present at birth were available from B-cells, a small amount of heparinized cord blood obtained from each newborn could be tested for the presence of the marker. Positive tests would identify the child as rheumatic fever susceptible individual (about 19% of the population). The mother would be notified that her child is at risk of contracting rheumatic fever and all of the child's sore throats would then be treated carefully for ten days, usually with penicillin. Those children who are not susceptible when infected with a streptococcal sore throat might be treated for a lesser period, i.e., 4 to 5 days. The cost savings are readily apparent.
Such identification tests, while important in relatively affluent countries, are of far greater importance in third world countries. In these countries, with their characteristically large and still growing populations, treatment of all streptococcal sore throats is realistically impossible and financially prohibitive. Identification of susceptible individuals at birth or early in childhood would allow health agencies in such countries to concentrate their efforts on those individuals at high risk. Obviously, an inexpensive method of identifying these individuals would be the optimal way to prevent long term chronic heart disease, one of the most unfortunate results of rheumatic fever. At the present time, a very high proportion of the public health budget is expended to treat symtopmatically and to sustain victims of long standing chronic heart disease resulting from rheumatic fever. Prevention is obviously a less expensive procedure.